The Air Quality Directive included a provision that allowed
member states to establish zones where it would be difficult to
reduce pollution.

According to the ECJ’s ruling last year, “a Member State may
postpone the deadline until 1 January 2015 at the latest.”

The ECJ ruled the British government must have a plan to meet
European air quality standards in the “shortest time
possible.”

UK courts were empowered by the ECJ to take any measure necessary
to ensure the government complies.

ClientEarth took the case to Britain’s Supreme Court on April 16
this year.

Under the government’s current planes, air pollution would not
reach legal levels in some British cities such as London,
Birmingham and Leeds until 2030.

The court’s ruling follows a day of high-to-very-high levels of
air pollution in Southern England earlier this month.

Asthma sufferers were advised they may need to use inhalers more
often and elderly people were warned to avoid physical exertion.

Campaigners at Clean Air in London cautioned those preparing for
last weekend’s marathon to “very seriously consider”
training indoors.

Alan Andrews, a lawyer for ClietnEarth, said: “This ruling
will benefit everyone's health but particularly children, older
people and those with existing health conditions like asthma and
heart and lung conditions.

“The next government, regardless of the political party or
parties which take power, is now legally bound to take urgent
action on this public health crisis.”

A spokesperson for the Department for Environment, Food and Rural
Affairs (Defra) said: “Air quality has improved significantly
in recent years and as this judgment recognizes, work is already
underway on revised plans (since February 2014) to meet EU
targets on NO2 as soon as possible.”

“It has always been the government's position to submit these
plans before the end of this year. Meeting NO2 limits is a common
challenge across Europe with 17 member states exceeding
limits.”